The present invention relates to a method and device for determining the operation balance of machines, and more particularly to a method and device which can determine the operation balance of NC machine tools, individually and for any arbitrary period, by monitoring and analyzing the actual processing status of such machine tools.
For processing or assembly of parts, specific machine tools or assembly machines are installed in various production facilities. According to the general plant management method conventionally adopted, initial costs including purchase prices and installation cost, as well as maintenance costs, are calculated as expenditure for individual machines and the share of their costs are assumed in the profit of the entire production organization.
However, it is simply not possible to correctly determine the contribution of individual machines by such rough assumption in conventional practices. For plant managers or top management, correctly understanding the operation balance of an individual machine has been an important problem.
In general, the operation balance of a machine can be determined by subtracting the maintenance/management costs for the machine including machine management costs, personnel expenses and depreciation costs from its profit. However, it has been impossible to continuously and automatically monitor the income and expenditure related to particular individual machines in conventional business. In particular, in light of the labor required for calculation, it is not realistic to calculate costs of consumables, such as tools and power rates, corresponding to the operation status of each machine.
An example of such machines is a machine tool controlled by a numerically controlled (NC) program. Many NC machine tools are used in various processing sites. It is well known that, in a CNC machine tool, a CNC device analyzes the program usually known as NC statements and controls the feed motor. A PLC (Programmable Logic Controller) device typically incorporated in a CNC device analyzes the program and simultaneously controls the spindle motor and mechanical sections of tool changer, workpiece changer or coolant device. In addition, it is known that some CNC machine tools incorporate an automatic programming device to automatically generate the NC statements and to send codes other than NC statements to the CNC device and the PLC device. The CNC or PLC device displays the operation hours and counts the number of processed workpieces as additional information when the above controls are executed.
However, even such advanced conventional CNC devices cannot calculate the balance between income and expenditure to grasp the operation status. The machine user remains unable to learn how a specific machine contributes to the balance on a real time basis.
The present invention develops the operation time indication or processed workpiece counting used in the conventional CNC devices as described above, detects machine operation statuses as operations related to income and expenditure of the machine by monitoring and analyzing the NC program execution statuses, and calculates the operation balance using them. As a result, the profit ratio of the machine over any arbitrary period can be determined making it possible to more effectively use the machine.
For this purpose, the present invention is characterized in that it detects income/expenditure-related machine operations as income/expenditure data, stores income/expenditure amounts in the memory based on the detected income/expenditure data, and, based on such stored income/expenditure amounts, calculates the income/expenditure balance of the individual machine over any arbitrary period.
Further, it may be useful to adopt machine tools controlled according to NC programs as such machines. By monitoring the NC program execution statuses, the operations related to income/expenditure of the machine tools can be detected as the income/expenditure data. In the present invention, income/expenditure data refers to the data obtained by detection of operations related to income/expenditure where income and expenditure are actually generated in each individual machine tool. In the case of NC machine tools, such data are detected from execution statuses of the NC program.
To determine the income/expenditure amounts from the income/expenditure data, the sales price of the processed product and the expenditure such as the material unit price and personnel expense unit price stored in advance in the income/expenditure price registration unit may be used. The income/expenditure balance data can be stored in the memory along with the date and time when such operation balance occurs. It may further be preferable to add the attribute information required to identify the type of the operation balance to the income/expenditure amounts stored in the memory.
In the present invention, the income/expenditure calculation is made for an arbitrary period basically by the operation to subtract the total expenditure from the total income. The arbitrarily selected period may be selected from predetermined periods, such as every week or every month. The income/expenditure calculation results for the individual periods are displayed on a display unit.
The operation balance items in the present invention preferably include the sales income and miscellaneous income as income items and expenditure items such as material costs, personnel expenses, power rates, depreciation costs, tool consumption costs, coolant/lubrication oil costs, maintenance charges, and miscellaneous costs.
In a method and device in which the present invention is applied, the machine for operation balance calculation may be a single unit, or may be several devices connected via network. The method to calculate the operation balance can be described as computer programs, which can be incorporated into CNC software or PLC software as applications for CNC device or can be incorporated to the personal computer section of open CNC.
When several machines are connected via a network as referenced to above, operation balances of various processes can be displayed and checked on a single computer by incorporating the operation balance calculation program into a PC connected to the network. This can be useful for control of machines, as well as monitoring and analysis of contribution ratios of the machines.
Referring to the attached drawings, preferred embodiments of the present invention will be described in detail below.